The long-lasting luminescence of transparent alumina and Tb3+–Zn2+(Ca2+) co-doped alumina films, prepared by using the aqueous sol-gel method, was examined. A strong luminescence of 300 to 500nm was observed for non-doped alumina, and was shown to depend upon the treatment temperature of the gel. The luminescence was not observed for alumina treated at temperatures higher than 600C. The luminescence band was composed of plural components due to O defect sites in alumina. The lasting luminescence of Tb3+–Zn2+(Ca2+) co-doped alumina were observed after irradiation for several seconds using an ultra-violet lamp (15W). The results indicated that the O defect sites of alumina served as a photoelectron trap center and that the AlV site served as a hole trap center, which could be thermally released at room temperature.

Creation of Long Lasting Luminescence in Transparent Aluminas. T.Ishizaka, Y.Kurokawa: Journal of Applied Physics, 2001, 90[5], 2257-61